When you open a Not As Described claim , the seller is given the choice of sending you return shipping and refunding on arrival or abandoning the disputed item and refunding immediately.
If they do neither- if they ignore your Claim through the Money Back Guarantee- eBay refunds you, goes after the seller for their money, and gives the seller a Defect which can lead to higher fees, restrictions on the number and value of future listings, or even a closed selling account.
You are also covered by the chargeback policy of the credit card you paid with.
Debit cards, e-transfers and wire transfers have no chargeback provisions, effectively, so online ONLY use a credit card for purchasing.
A No Returns policy is not a No Refunds policy.
They are not even spelled the same.